Portable electrical energy storage device with in-situ formable fluid channels

ABSTRACT

An electrical energy storage device for powering portable devices such as vehicles or consumer electronics includes barriers to minimize migration of thermal energy and propagation of combustion in the rare event that electrical energy storage cells fail, burst and ignite. Thermal energy absorbing materials are contained within the electrical energy storage device. Sacrificial members are provided within the thermal energy absorbing materials. In-situ channels are formed within the thermal energy absorbing materials when the sacrificial members thermally decompose.

BACKGROUND Technical Field

The embodiments described herein relate to portable electrical energystorage devices, such as those used in electric powered devices such asvehicles, and consumer electronics and thermal runaway mitigationsystems for such portable electrical energy storage devices.

Description of the Related Art

Batteries such as lithium-ion batteries are known for packing moreenergy into smaller, lighter units. Lithium-ion batteries have foundwide application in powering portable electronic devices such as cellphones, tablets, laptops, power tools and other high-current equipment.The low weight and high energy density also makes lithium-ion batteriesattractive for use in hybrid vehicles and fully electric-poweredvehicles.

A potential shortcoming of lithium-ion batteries is their electrolytesolutions. Unlike other types of batteries, in which the electrolytesconsist of aqueous solutions of acid or base, the electrolyte inlithium-ion cells typically consists of lithium salts in organicsolvents such as ethylene carbonate and ethyl methyl carbonate (whichcan be flammable).

Under normal operation, charging a lithium-ion battery causes lithiumions in the electrolyte solution to migrate from the cathode through athin porous polymer separator and insert themselves in the anode. Chargebalancing electrons also move to the anode but travel through anexternal circuit in the charger. Upon discharge, the reverse processoccurs, and electrons flow through the device being powered.

In very rare circumstances, internal or external short-circuiting of alithium-ion battery can occur. For example, the electric-powered devicecontaining the lithium-ion battery can undergo a severe impact or shockresulting in a breach in the battery, which could result in a shortcircuit. Due to the thin nature of the polymer separator,micrometer-sized metal particles generated during cutting, pressing,grinding, or other battery manufacturing steps can be present or findtheir way into the battery cell. These small metal particles canaccumulate and eventually form a short circuit between the anode and thecathode. Such short circuits are to be avoided because they can resultin temperatures at which the cathode may react with and decompose theelectrolyte solution, generating heat and reactive gases such ashydrocarbons. Typically, at normal operating temperatures, lithium-ionbatteries are very stable; however, above a certain temperature,lithium-ion battery stability becomes less predictable, and at anelevated temperature, chemical reactions within the battery case willproduce gases resulting in an increase in the internal pressure withinthe battery case. These gases can react further with the cathode,liberating more heat and producing temperatures within or adjacent tothe battery that can ignite the electrolyte in the presence of oxygen.When the electrolyte burns, small amounts of oxygen are produced, whichmay help fuel the combustion. At some point, build-up of pressure withinthe battery case results in the battery case rupturing. With exposure tofurther oxygen, the escaping gas may ignite and combust. Some batterymanufacturers design their cells so, in the unlikely event a cellruptures and ignites, gases that support combustion exit the cell inpredetermined locations and directions. For example, battery cells inthe shape of conventional AAA or AA cells may be designed to vent fromthe terminal ends located at each end of the cell.

In applications where only a single lithium-ion battery is utilized,failure of a battery and the potential for combustion creates anundesirable situation. The severity of this situation is increased whena plurality of lithium-ion batteries are deployed in the form of abattery bank or module. The combustion occurring when one lithium-ionbattery fails may produce local temperatures above the temperature atwhich other lithium-ion batteries are normally stable, causing theseother batteries to fail, rupture, and vent gases which then ignite andcombust. Thus, it is possible for the rupture of a single cell in a bankof lithium-ion cells to cause other cells in the bank to rupture anddischarge gases which ignite and burn. Fortunately, lithium-ionbatteries have proven to be very safe, and the failure and consequentrupture of a lithium-ion battery is a very rare event. Nonetheless,efforts have been made to reduce the risk of rupture and ignition ofgases exiting a ruptured lithium-ion battery. For example, developmentof materials used for cathodes has produced lithium-based cathodematerials that tolerate heat better than cathodes made from the widelyused lithium cobalt oxide. While these more recently developed materialsmay be more heat tolerant, this benefit comes at a price. For example,lithium manganese oxide cathodes have a lower charge capacity thanlithium cobalt oxide and still decompose at high temperatures. Lithiumiron phosphate cathodes stand up especially well to thermal abuse;however, their operating voltage and energy density on a volume basisare lower than those of lithium cobalt oxide cathodes.

Other efforts have focused on the polymer separator and its design. Forexample, it has been proposed to utilize a polymer separator thatsandwiches a layer of polyethylene between two layers of polypropylenein an effort to provide a degree of protection against mild overheating.As the temperature of the cell begins to approach that at which thestability of the cell becomes unpredictable, the polyethylene melts andplugs the pores in the polypropylene. When the pores of a polypropyleneare plugged by the polyethylene, lithium diffusion is blocked,effectively shutting the cell down before it has a chance to ignite.Other efforts have focused on utilizing polymer separators havingmelting points higher than polypropylene. For example, separators madefrom polyimides and separators made from high molecular weightpolyethylene and an embedded ceramic layer have been proposed to form arobust higher melting point polymer separator. Formulating and utilizingless flammable electrolytes and nonvolatile, nonflammable ionic liquids,fluoroethers, and other highly fluorinated solvents as batteryelectrolytes have also been investigated. Researchers have developedlithium-ion batteries that contain no liquids at all. These solid-statebatteries contain inorganic lithium-ion conductors, which are inherentlynonflammable and are thus very stable, safe, and exhibit long cycle lifeand shelf life. However, the manufacture of these solid-state batteriesrequires costly, labor-intensive vacuum deposition methods.

Despite these efforts, there continues to be a need for a portableelectrical energy storage device that effectively manages the risk ofelectrical energy storage cell failure and combustion of gases producedas a result of such failure in multi-cell deployments, as well aspropagation of failure inducing thermal energy to battery cells adjacenta failed cell, and the hazard to the user in the event of such a rareevent.

BRIEF SUMMARY

Embodiments described in this application relate to portable electricalenergy storage devices and methods of making portable electrical energystorage devices that include sacrificial members within the portableelectrical energy storage device which are capable of thermallydecomposing. Upon thermal decomposition of the sacrificial members,channels are formed within the portable electrical energy storage devicethrough which gases resulting from failure of an electrical energystorage cell can pass.

In embodiments of one aspect of the subject matter described, the methodof manufacturing a portable electrical energy storage device includesproviding, within a portable electrical energy storage device housing, afirst electrical energy storage cell module including a plurality ofelectrical energy storage cells and a second electrical energy storagecell module including a plurality of electrical energy storage cellsadjacent the first electrical energy storage cell module. In accordancewith these embodiments, a thermal energy absorbing material is providedin the housing and a sacrificial member provided within the housing andwithin the thermal energy absorbing material. The sacrificial member isformed of a material that does not thermally decompose when exposed toan environment below a first temperature and thermally decomposes whenexposed to an environment at a second temperature greater than the firsttemperature.

In further embodiments of methods described herein, another sacrificialmember formed of a material that does not thermally decompose whenexposed to an environment below a first temperature and thermallydecomposes when exposed to an environment at a second temperaturegreater than the first temperature is provided. The other sacrificialmember is located between the portable electrical energy storage devicehousing and both the first electrical energy storage cell module and thesecond electrical energy storage cell module.

Other embodiments described in this application relate to portableelectrical energy storage devices including a first electrical energystorage cell module including a plurality of electrical energy storagecells, a second electrical energy storage cell module including aplurality of electrical energy storage cells, the second electricalenergy storage cell module positioned adjacent the first electricalenergy storage cell module, a thermal energy absorbing material, and asacrificial member formed of a material that does not thermallydecompose when exposed to an environment below a first temperature andthermally decomposes when exposed to an environment at a secondtemperature greater than the first temperature, the sacrificial memberlocated within the thermal energy absorbing material. In someembodiments, the described portable electrical energy storage devicesinclude a portable electrical energy storage device housing with thefirst electrical energy storage cell module and the second electricalenergy storage cell module located within the housing and anothersacrificial member formed of a material that does not thermallydecompose when exposed to an environment below a first temperature andthermally decomposes when exposed to an environment at a secondtemperature greater than the first temperature. This other sacrificialmember is located between the portable electrical energy storage devicehousing and both the first electrical energy storage cell module and thesecond electrical energy storage cell module.

Additional embodiments described in this application relate to aportable electrical energy storage devices including a portableelectrical energy storage device housing, a first electrical energystorage cell module including a plurality of electrical energy storagecells and located within the portable electrical energy storage devicehousing, a second electrical energy storage cell module including aplurality of electrical energy storage cells and located within theportable electrical energy storage device housing, the second electricalenergy storage cell module positioned adjacent the first electricalenergy storage cell module, a third electrical energy storage cellmodule including a plurality of electrical energy storage cells andlocated within the portable electrical energy storage device housing,the third electrical energy storage cell module positioned adjacent thesecond electrical energy storage cell module on a side of the secondelectrical energy storage cell module opposite from the first electricalenergy storage cell module. The portable electrical energy storagedevice further includes a thermal energy absorbing material and asacrificial member within the thermal energy absorbing material, thesacrificial member formed of a material that does not thermallydecompose when exposed to an environment below a first temperature andthermally decomposes when exposed to an environment at a secondtemperature greater than the first temperature. In some embodiments, thedescribed portable electrical energy storage devices include a portableelectrical energy storage device housing with the first electricalenergy storage cell module and the second electrical energy storage cellmodule located within the housing and another sacrificial member formedof a material that does not thermally decompose when exposed to anenvironment below a first temperature and thermally decomposes whenexposed to an environment at a second temperature greater than the firsttemperature. This other sacrificial member is located between theportable electrical energy storage device housing and both the firstelectrical energy storage cell module and the second electrical energystorage cell module

Other embodiments described in this application relate to portableelectrical energy storage devices that include an electrical energystorage cell barrier that functions as a thermal isolator and thermalbarrier to propagation of cell failure inducing thermal energy. Theelectrical energy storage cell barrier also includes an elastic materialfunctioning to protect terminals of electrical energy storage cells fromdamage, acting as an electrical isolator and serving as a shock absorberto protect the electrical energy storage cells from damage resultingfrom an impact or other force.

In embodiments of one described aspect, a portable electrical energystorage device includes a first electrical energy storage cell, a secondelectrical energy storage cell, and an electrical energy storage cellbarrier comprising a thermal insulating material and an elasticmaterial, the electrical energy storage cell barrier located between thefirst electrical energy storage cell and the second electrical energystorage cell.

In embodiments of another described aspect, the first electrical energystorage cell comprises a plurality of first electrical energy storagecells.

In other embodiments, the second electrical energy storage cellcomprises a plurality of second electrical energy storage cells.

In yet another embodiment, the second electrical energy storage cell isadjacent the first electrical energy storage cell.

Though not limited to the following chemistries, the first electricalenergy storage cell may comprise nickel-metal hydride chemistry orlithium-ion chemistry and the second electrical energy storage cell maycomprise the same chemistry as the first electrical energy storage cell.

In certain embodiments, the electrical energy storage cell barriercomprises a layer of thermal insulating material and a layer of elasticmaterial and/or one layer of the thermal insulating material between twolayers of the elastic material. In specific embodiments, the thermalinsulating material has a coefficient of thermal conductivity less thanabout 0.5 BTU/ft²/hr/inch and preferably 0.5 BTU/ft²/hr/inch attemperatures where ignition of failed cells occurs. The thermalinsulating material may include ceramic materials, vermiculite-basedmaterials or other materials known to provide thermal insulatingproperties. The carrier for the ceramic materials may be paper-based,ceramic impregnated cloths, fiberglass or other materials capable ofbeing formed into thin sheets containing thermal insulating materials. Aspecific example of a thermal insulating material is one that includesceramic fiber, such as a ceramic fiber paper. Examples of suitableceramic fibers include alumina, mullite, silicon carbide, zirconia orcarbon.

Examples of elastic material include rubber, and more specifically,fluoropolymer rubber, butyl rubber, chlorosulfonated polyethylenerubber, epichlorohydrin rubber, ethylene propylene rubber,fluoroelastomer rubber, fluorosilicone rubber, hydrogenated nitrilerubber, natural rubber, nitrile rubber, perfluoroelastomer rubber,polyacrylic rubber, polychloroprene rubber, polyurethane rubber,silicone rubber and styrene butadiene rubber

In embodiments of another described aspect, a portable electrical energystorage device includes a first electrical energy storage cell moduleincluding a plurality of electrical energy storage cells and a secondelectrical energy storage cell module including a plurality ofelectrical energy storage cells, the second electrical energy storagecell module positioned adjacent the first electrical energy storage cellmodule. This portable electrical energy storage device also includes afirst electrical energy storage cell barrier comprising a thermalinsulating material and an elastic material located between the firstelectrical energy storage cell module and the second electrical energystorage cell module, a second electrical energy storage cell barriercomprising a thermal insulating material and an elastic material locatedadjacent the second electrical energy storage cell module, and a thirdelectrical energy storage cell barrier comprising an elastic material,the third electrical energy storage cell barrier positioned adjacent thefirst electrical energy storage cell module.

In certain embodiments of this described aspect, the thermal insulatingmaterial of the first electrical energy storage cell barrier is betweentwo layers of the elastic material of the first electrical energystorage cell barrier. In yet other embodiments, the elastic material ofthe second electrical energy storage cell barrier is between the thermalinsulating material of the second electrical energy storage cell barrierand the second electrical energy storage cell module.

In additional embodiments of this aspect, the portable electrical energystorage device includes a third electrical energy storage cell moduleadjacent the second electrical energy storage cell module and a fourthelectrical energy storage cell barrier comprising a thermal insulatingmaterial and an elastic material positioned adjacent the thirdelectrical energy storage cell module. In these additional embodiments,the thermal insulating material of the fourth electrical energy storagecell barrier is separated from the third electrical energy storage cellbarrier by a layer of the elastic material of the fourth electricalenergy storage cell barrier.

In embodiments of a further aspect described in the present application,a portable electrical energy storage device includes a housing includinga cover and a base. At least one electrical energy storage cell moduleincluding a plurality of electrical energy storage cells is contained inthe housing and an electrical energy storage cell barrier including athermal insulating material and an elastic material is located adjacentthe cover with the thermal insulating material located between the coverand the elastic material. An elastic material is located adjacent thebase and is between the electrical energy storage cell module and thebase.

In accordance with embodiments of various aspects described in thepresent application, a portable electrical energy storage deviceincludes a burst structure that remains intact when pressure within theportable electrical energy storage device is below a maximum internalpressure and ruptures when pressure within the portable electricalenergy storage device exceeds the maximum internal pressure.

In embodiments of another described aspect, a portable electrical energystorage device includes a housing including a cover and a base. A firstelectrical energy storage cell module including a plurality ofelectrical energy storage cells and a second electrical energy storagecell module including a plurality of electrical energy storage cells arecontained within the housing, with the second electrical energy storagecell module positioned adjacent the first electrical energy storage cellmodule. A third electrical energy storage cell module including aplurality of electrical energy storage cells is included in the housingand is positioned adjacent the second electrical energy storage cellmodule on a side of the second electrical energy storage cell moduleopposite from the first electrical energy storage cell module. A firstelectrical energy storage cell barrier including a thermal insulatingmaterial sandwiched between an elastic material is located between thefirst electrical energy storage cell module and the second electricalenergy storage cell module. A second electrical energy storage cellbarrier including a thermal insulating material sandwiched between anelastic material is located between the second electrical energy storagecell module and the third electrical energy storage module. A thirdelectrical energy storage cell barrier including an elastic material islocated between the first electrical energy storage cell module and thebase and a fourth electrical energy storage cell barrier including athermal insulating material and an elastic material is located betweenthe third electrical energy storage cell module and the cover.

In another described embodiment, a portable electrical energy storagedevice includes a housing including a sidewall and a first electricalenergy storage cell module including a plurality of electrical energystorage cells and located within the housing. A second electrical energystorage cell module including a plurality of electrical energy storagecells is also located within the housing adjacent the first electricalenergy storage cell module. The portable electrical energy storagedevice includes a first electrical energy storage cell barriercomprising an electrical isolation layer of a dielectric materialsandwiched between an electrical energy storage cell contact protectionlayer of an elastic material and a combustion barrier layer of anon-combustible material. The first electrical energy storage cellbarrier is located between the first electrical energy storage cellmodule and the second electrical energy storage cell module. Theelectrical isolation layer of dielectric material of the firstelectrical energy storage cell barrier includes at least one biased ventand the combustion barrier layer of a non-combustible material of thefirst electrical energy storage cell barrier includes at least onebiased vent. The portable electrical energy storage device furtherincludes a second electrical energy storage cell barrier comprising anelectrical isolation layer of a dielectric material sandwiched betweenan electrical energy storage cell contact protection layer of an elasticmaterial and a combustion barrier layer of a non-combustible material.The electrical isolation layer of dielectric material of the secondelectrical energy storage cell barrier includes at least one biased ventand the combustion barrier layer of a non-combustible material of thesecond electrical energy storage cell barrier includes at least onebiased vent. The second electrical energy storage cell barrier islocated between the second electrical energy storage cell module and thefirst electrical energy storage cell barrier. In accordance with thisdescribed embodiment, the at least one biased vent included in theelectrical isolation layer of dielectric material of the firstelectrical energy storage cell barrier and the at least one biased ventincluded in the combustion barrier layer of a non-combustible materialof the first electrical energy storage cell barrier are biased to aclosed position and movable from the closed position to an openposition, the closed position impeding the flow of gas through the firstelectrical energy storage cell barrier and the open position impedingthe flow of gas through the first electrical energy storage cell barrierto a lesser degree than the closed position. The at least one biasedvent included in the electrical isolation layer of dielectric materialof the second electrical energy storage cell barrier and the at leastone biased vent included in the combustion barrier layer of anon-combustible material of the second electrical energy storage cellbarrier are biased to a closed position and movable from the closedposition to an open position, with the closed position impeding the flowof gas through the second electrical energy storage cell barrier and theopen position impeding the flow of gas through the second electricalenergy storage cell barrier to a lesser degree than the closed position.

In embodiments of a further aspect of a portable electrical energystorage cell device described herein, the portable electrical energystorage device includes a housing including a sidewall with a firstelectrical energy storage cell module including a plurality ofelectrical energy storage cells located within the housing. A secondelectrical energy storage cell module including a plurality ofelectrical energy storage cells is also located within the housing andadjacent the first electrical energy storage cell module. A firstelectrical energy storage cell barrier comprising a layer of adielectric material sandwiched between a layer of an elastic materialand a layer of a non-combustible material is located between the firstelectrical energy storage cell module and the second electrical energystorage cell module. The layer of dielectric material of the firstelectrical energy storage cell barrier includes at least one biased ventand the layer of a non-combustible material of the first electricalenergy storage cell barrier includes at least one biased vent. The atleast one biased vent included in the layer of dielectric material ofthe first electrical energy storage cell barrier and the at least onebiased vent included in the layer of a non-combustible material of thefirst electrical energy storage cell barrier are biased to a closedposition and movable from the closed position to an open position, withthe closed position impeding the flow of gas through the firstelectrical energy storage cell barrier and the open position impedingthe flow of gas through the first electrical energy storage cell barrierto a lesser degree than the closed position.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not drawn to scale, and some of these elementsare arbitrarily enlarged and positioned to improve drawing legibility.Further, the particular shapes of the elements as drawn, are notintended to convey any information regarding the actual shape of theparticular elements, and have been solely selected for ease ofrecognition in the drawings.

FIG. 1 is an isometric, partially exploded view of a portable electricalenergy storage device that includes some of the various components orstructures described herein, according to one non-limiting illustratedembodiment.

FIG. 2 is an isometric, more fully exploded view of the portableelectrical energy storage device of FIG. 1.

FIG. 3 is an isometric, partially exploded view of another embodiment ofa portable electrical energy storage device that includes some of thevarious components or structures described herein, according to onenon-limiting illustrated embodiment.

FIG. 4 is an isometric view of burst structures formed in accordancewith one non-limiting illustrated embodiment.

FIG. 5 is a schematic illustration of an electrical energy storagedevice in accordance with non-limiting embodiments described hereinillustrating potential paths taken by gas and thermal energy emanatingfrom a failed electrical energy storage cell of an electrical energystorage cell module.

FIG. 6 is an exploded view of an electrical energy storage cell moduleof a portable electrical energy storage device that includes some of thevarious components or structures described herein, according tonon-limiting embodiments described herein.

FIG. 7 is a side elevation view of a portable electrical energy storagedevice that includes two electrical energy storage cell modules of thetype illustrated in FIG. 6.

FIG. 8 is an isometric view of a portion of an electrical energy storagecell module with biased vents in a closed position, according to anon-limiting embodiment.

FIG. 9 is an isometric view of the electrical energy storage cell moduleof FIG. 8 showing the biased vents in an open position.

DETAILED DESCRIPTION

It will be appreciated that, although specific embodiments of thesubject matter of this application have been described herein forpurposes of illustration, various modifications may be made withoutdeparting from the spirit and scope of the disclosed subject matter.Accordingly, the subject matter of this application is not limitedexcept as by the appended claims.

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedembodiments. However, one skilled in the relevant art will recognizethat embodiments may be practiced without one or more of these specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures associated with portable electricalenergy storage cells, e.g., batteries, have not been shown or describedin detail to avoid unnecessarily obscuring descriptions of theembodiments.

Unless the context requires otherwise, throughout the specification andclaims which follow, the word “comprise” and variations thereof, suchas, “comprises” and “comprising” are to be construed in an open,inclusive sense that is as “including, but not limited to.”

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. Thus, the appearances of the phrases “in one embodiment” or“in an embodiment” in various places throughout this specification arenot necessarily all referring to the same embodiment.

The use of ordinals such as first, second and third does not necessarilyimply a ranked sense of order, but rather may only distinguish betweenmultiple instances of an act or structure.

Reference to portable electrical power storage device or electricalenergy storage device means any device capable of storing electricalpower and releasing stored electrical power including, but not limitedto, batteries, supercapacitors or ultracapacitors, and modules made upof a plurality of the same. Reference to portable electrical energystorage cell(s) means a chemical storage cell or cells, for instance,rechargeable or secondary battery cells including, but not limited to,nickel-cadmium alloy battery cells or lithium-ion battery cells. Anon-limiting example of portable electrical energy storage cells isillustrated in the figures as being cylindrical, e.g., similar in sizeand shape to conventional AAA size batteries; however, the presentdisclosure is not limited to this illustrated form factor.

The headings and Abstract of the Disclosure provided herein are forconvenience only and do not interpret the scope or meaning of theembodiments.

Generally described, the present disclosure is directed to examples ofportable electrical energy storage devices suitable to power electricdevices such as electric powered or hybrid type vehicles, e.g.,motorcycles, scooters and electric bicycles, electric powered tools,electric powered lawn and garden equipment, and the like, which includeone or more electrical energy storage cell barriers that serve toprevent migration and propagation of electrical energy storage celldestabilizing thermal energy from one electrical energy storage cell ormodule to another electrical energy storage cell or module. Furtherdescription of portable electrical energy storage devices in accordancewith embodiments described herein is provided in the context of portableelectrical energy storage devices used with electric scooters; however,it should be understood that portable electrical energy storage devicesin accordance with embodiments described herein are not limited toapplications in electric scooters. In addition, portable electricalenergy storage devices are described below with reference to a singleelectrical energy storage cell module containing a plurality ofelectrical energy storage cells and a pair of electrical energy storagecell modules each containing a plurality of electrical energy storagecells. The present description is not limited to electrical energystorage devices that include only a single electrical energy storagecell module or only a pair of electrical energy storage cell modules andencompasses portable electrical energy storage devices that include morethan a pair of electrical energy storage cell modules.

In a specific application wherein portable electrical energy storagedevices in accordance with embodiments described in the presentapplication are utilized to power electric vehicles, such as an electricscooter, one or more portable electrical energy storage device isreceived in a compartment located beneath the user, e.g., under the seatof the scooter. Typically, the portable electrical energy storage deviceincludes a handle by which the user carries the portable electricalenergy storage device and places it into and removes it from thecompartment.

Referring to FIG. 1, a portable electrical energy storage device 10includes an electrical energy storage cell module 12 including aplurality of individual electrical energy storage cells 14. Theelectrical energy storage cell module 12 is housed within a housing 16that includes a shell 18, a cover 20, and a base 22. Shell 18, cover 20and base 22 are formed from the same or different rigid noncombustiblematerial, such as a metal or non-metal such as a plastic. An exemplarynon-limiting example of a metal is aluminum. Though not illustrated,cover 20 may include a handle to facilitate carrying of the electricalenergy storage device. Also, though not illustrated, base 22 includeselectrically conductive elements passing through shell 18 andcooperating with electrically conductive elements within shell 18 toprovide electrical connection to electrical energy storage cell module12 from a location external to portable electrical energy storage device10. In addition, electrically conductive elements are associated witheach electrical energy storage cell module and electrically connectindividual electrical energy storage cells and also electrically connectelectrical energy storage cell modules. Shell 18 is sealed in agas-tight manner to cover 20 and to base 22 and forms a gas-tighthousing. The electrically conductive elements passing through base 22are also sealed in a gastight manner to base 22. Thus, shell 18, cover20, and base 22 form a gas-tight enclosure containing electrical energystorage cell module 12. Because the shell 18, cover 20 and base 22 forma gastight enclosure, the enclosure can be evacuated to removecombustion supporting oxygen. Removing combustion supporting oxygenreduces the amount of combustion that can occur within the sealedenclosure. Alternatively, the enclosure can be purged of combustionsupporting oxygen by displacing oxygen with gases incapable ofsupporting combustion, such as nitrogen. Shell 18 can be sealed to cover20 and base 22 using conventional materials such as mating female andmale members alone or in combination with adhesive materials.Alternatively or additionally, gaskets can be provided to seal shell 18to cover 20 and base 22. Similarly, the electrically conductive elementspassing through base 22 can be sealed to base 22 using conventionalmaterials such as adhesive materials and/or gaskets.

The interstices between adjacent electrical energy storage cells 14making up electrical energy storage cell module 12, and void spacebetween electrical energy storage cells 14 and housing 16, are occupiedby a thermal energy absorbing material capable of latent heat storage.Suitable thermal energy absorbing materials absorb or release thermalenergy without a substantial change in temperature of the material,e.g., through a phase change. Examples of thermal energy absorbingmaterials include materials capable of absorbing and storing largeamounts of energy via a phase change. Such materials are commonlyreferred to as phase change materials. Phase change materials aregenerally understood to be limited to materials wherein the phase changeis between a solid and a liquid; however, phase change materials are notlimited to those that change between a solid and a liquid state. Phasechange materials can be organic materials, such as paraffins and fattyacids. Phase change materials can also be inorganic, such as salthydrates. Phase change materials can also be eutectic materials orhygroscopic materials.

As noted in the Background, though rare, internal or externalshort-circuiting of lithium-ion electrical energy storage cells canresult in the temperature of an individual electrical energy storagecell increasing to a level at which the cathode may react with anddecompose the electrolyte solution. If this occurs, additional thermalenergy is produced and the gases that are produced from thedecomposition of the electrolyte solution can react with the cathode,liberating more thermal energy. The production of gases within anelectrical energy storage cell causes the pressure within the sealedcell to increase. If the pressure within the cell increases above thedesigned cell burst pressure, the cell ruptures and the gas escapes.During these reactions, a limited amount of oxygen is produced which cansupport further combustion. If the escaping gases are exposed totemperatures above that at which the gases ignite, the gases may igniteand combust. In addition, if the thermal energy released from oneshort-circuited cell and the combustion of gases escaping a burst cellcause the temperature of other electrical energy storage cells to riseabove a temperature at which such cells are normally stable, cathodes ofthese other electrical energy storage cells may then react with theelectrolyte solution and produce gases that cause these cells to burstand combust. Though such short circuit initiated combustion is rare,good design and concern for the safety of the user dictates that stepsbe taken to protect users in the unlikely event electrical energystorage cells fail.

Continuing to refer to FIG. 1 and referring additionally to FIG. 2, onenon-limiting embodiment of one aspect of a portable electrical energystorage device described herein includes a single electrical energystorage cell module 12 including a plurality of electrical energystorage cells 14. In the embodiment illustrated in FIG. 1, the singleelectrical energy storage cell module 12 includes multiple individualelectrical energy storage cells 14. It should be understood that agreater number or a lesser number of individual electrical energystorage cells may be utilized compared to the number illustrated in FIG.1.

Though not specifically illustrated in order to avoid obscuring otherfeatures of the disclosed subject matter, the interstices betweenelectrical energy storage cells 14 are occupied by a phase changematerial. The specific phase change material utilized is selected takinginto consideration a number of factors, including the magnitude ofthermal energy the phase change material is able to absorb beforecompleting its phase change and its temperature beginning to rise.Generally, phase change materials that are able to absorb more energybefore the change of state is completed are preferred over phase changematerials that complete the change of state upon absorbing less thermalenergy. Exemplary phase change materials include organic materials, suchas paraffins and fatty acids. Phase change materials can also beinorganic, such as salt hydrates. Phase change materials can also beeutectic materials or hygroscopic materials. In the embodimentillustrated in FIGS. 1 and 2, an electrical energy storage cell barrier24 is located above electrical energy storage cell module 12. Electricalenergy storage cell barrier 24 includes a layer of thermal insulatingmaterial 26 and a layer of elastic material 28. Both the layer ofthermal insulating material 26 and the layer of elastic material 28 aresized so as to overlap the entire upper surface of the electrical energystorage cell module 12. The periphery of the layer of thermal insulatingmaterial 26 and the periphery of the layer of elastic material 28 isshaped and sized to fit closely within shell 18. The close fit betweenthe layer of elastic material 28 and the layer of thermal insulatingmaterial 26 need not be so closely toleranced that a gastight seal isprovided between these layers and the internal surface of shell 18;however, the closer the fit between the inner surface of shell 18 and atleast one of the layer of thermal insulating material 26 and the layerof elastic material 28, the better the electrical energy storage cellbarrier 24 is able to block thermal energy and flames from combustionpassing between the inner surface of shell 18 and the outer periphery ofthe thermal insulating material 26 and/or the elastic material 28. Aless close fit between the inner surface of shell 18 and at least one ofthe layer of thermal insulating material 26 and the layer of elasticmaterial 28 would be preferred from the standpoint of ensuring the phasechange material or other fluid can flow between electrical energystorage cell barrier 24 and shell 18. The cooperation between the layerof thermal insulating material 26 and/or the layer of elastic material28 and the inner surface of shell 18 impedes and in some embodiments,more preferably prevents migration of thermal energy and flames fromcombustion of an electrical energy storage cell 14 in the electricalenergy storage cell module 12 to locations on the side of the electricalenergy storage cell barrier 24 opposite the side adjacent to theelectrical energy storage cell module 12. In other embodiments,cooperation between the layer of thermal insulating material 26 and/orthe layer of elastic material 28 and the inner surface of shell 18impedes migration of thermal energy and flames from combustion of anelectrical energy storage cell 14 in the electrical energy storage cellmodule 12 to locations on the side of the electrical energy storage cellbarrier 24 opposite the side adjacent to the electrical energy storagecell module 12, while allowing gases to flow from one side of theelectrical energy storage cell barrier 24.

Thermal insulating material 26 serves as a thermal insulation layer andbarrier to migration of thermal energy produced by combustion of anelectrical energy storage cell within electrical energy storage cellmodule 12 to the side of the layer of thermal insulating material 26that is opposite electrical energy storage cell module 12. By providinga barrier to migration of thermal energy from one side of electricalenergy storage cell barrier 24 to the other side, propagation of failureof electrical energy storage cells induced by elevated temperatures isreduced or avoided. The thermal insulating material 26 is chosen frommaterials that have a thermal conductivity such that the thermalinsulating material impedes the transfer of thermal energy through thethermal insulating material. In yet other non-limiting examples, thermalinsulating material 26 is formed from a material that is electricallynonconductive. The electrically nonconductive property of thermalinsulating material 26 prevents the thermal insulating material fromadversely affecting, e.g., short-circuiting, conductive featureselectrically connected to the electrical energy storage cells 14.Non-limiting examples of thermal insulating material 26 includematerials that have a thermal conductivity that is less than about 0.5BTU/ft²/hr/inch at temperatures corresponding to temperatures where theelectrical energy storage cells vent and ignition occurs. In addition,the thermal insulating material is also fire resistant at temperaturesgreater than about 130° C. The thermal insulating material may includeceramic materials, vermiculite-based materials or other materials knownto provide thermal insulating properties. The carrier for the ceramicmaterials may be paper-based, ceramic impregnated cloths, fiberglass orother materials capable of being formed into thin sheets containingthermal insulating materials. Non-limiting examples of thermalinsulating material include materials comprising ceramic fibers. Suchceramic fibers can be formed from alumina, mullite, silicon carbide,zirconia or carbon. In specific embodiments, the layer of thermalinsulating material 26 includes ceramic fibers in a paper-like form.Though not intending to be limited to such, some ceramic paper materialsare fire resistant to 1260° C. or higher. According to embodimentsillustrated in FIGS. 1 and 2, the layer of thermal insulating material26 has a thickness ranging from about 0.5 mm to about 2 mm, thoughthermal insulating material may be thicker or thinner depending on,among other things, the amount of thermal insulation desired.

Elastic material 28 serves as a combustion barrier by providing aphysical non-combustible barrier to migration of combustion of anelectrical energy storage cell 14 within electrical energy storage cellmodule 12 to the side of the energy storage cell barrier 24 opposite theelectrical energy storage cell module 12. Non-limiting examples ofmaterials for the layer of elastic material 28 include elastic materialsthat are noncombustible at temperatures of about 130° C. and higher. Innon-limiting embodiments, elastic material 28 provides protection toterminals of the electrical energy storage cells 14 by being formed froma material that is softer than the material from which the electricalenergy storage cell terminals are formed. In yet other non-limitingexamples, elastic material 28 is formed from a material that iselectrically nonconductive. The electrically nonconductive property ofelastic material 28 prevents the elastic material from adverselyaffecting, e.g., short-circuiting, conductive features electricallyconnected to the electrical energy storage cells 14. Non-limitingexamples of materials for elastic material 28 include materials thathave a hardness less than about 50 to 100 on a Shore scale and anelectrical resistivity of greater than about 10 to about 20 ohms ormore. In specific embodiments, elastic material is a fluoropolymerrubber, butyl rubber, chlorosulfonated polyethylene rubber,epichlorohydrin rubber, ethylene propylene rubber, fluoroelastomerrubber, fluorosilicone rubber, hydrogenated nitrile rubber, naturalrubber, nitrile rubber, perfluoroelastomer rubber, polyacrylic rubber,polychloroprene rubber, polyurethane rubber, silicone rubber and styrenebutadiene rubber. According to embodiments illustrated in FIGS. 1 and 2,the layer of elastic material 28 is about 0.5 mm to 2.0 mm thick, thoughelastic material may be thicker or thinner, depending, among otherthings, on the amount of combustion migration inhibition and/or shockabsorption desired.

As described in the Background, in applications where only a singleelectrical energy storage cell is utilized, combustion of the cellcreates an undesirable situation. The severity of this situation isincreased when a plurality of electrical energy storage cells aredeployed in the form of a battery bank or module. For example, when theelectrical energy storage cell includes lithium-ion chemistry,combustion of the lithium-ion cell can produce local temperatures abovethe temperature at which lithium-ion cells become unstable, burst andcombust. Thus, it is possible for the combustion of a single lithium-ioncell in a bank of lithium-ion cells to cause other cells in the bank toburst, ignite and burn. Fortunately, lithium-ion cells have proven to bevery safe and bursting and combustion of lithium-ion cells is very rare.Nonetheless, in the interest of user safety and acceptance of electricalenergy storage cells as power sources for electric vehicles, such asscooters, it is important to take steps to reduce the already lowlikelihood of bursting and combustion of a lithium-ion electrical energystorage cell and to manage combustion in the unlikely event that such acell should ignite.

In accordance with embodiments described herein, combustion of anelectrical energy storage cell or combustion of a plurality ofelectrical energy storage cells is managed through a combination of thefollowing features of embodiments described herein. First, advantage istaken of the need for oxygen to initiate ignition of gases from a burstcell and maintain combustion of an ignited cell. Second, in the eventcombustion occurs, migration of thermal energy from a failed andpotentially combusting cell to other cells is restricted. Third, up to acertain threshold pressure, gases formed as a result of cell failure andgases formed from the combustion of such gases are contained within theairtight sealed electrical energy storage device. Fourth, bursting ofthe electrical energy storage device is controlled to avoid uncontrolledbursting in unpredictable and potentially dangerous directions.

At a first level, containing lithium-ion electrical energy storage cellsin an oxygen free airtight housing isolates the cells from oxygennecessary to ignite and sustain combustion of flammable gases that mayexit a burst failed cell. Thus, in the unlikely event of a single cellfailure resulting in bursting of the cell and ignition of gas ventedfrom the cell, oxygen available to sustain combustion is limited tooxygen produced by reactions occurring between reactants within thefailed cell. Limiting the oxygen available to support combustion to theoxygen generated in situ minimizes the length of time combustion withinthe electrical energy storage device occurs, thereby reducing thelikelihood the temperature within the device will be elevated to a levelwhere failure and subsequent bursting and combustion of gases from othercells occurs. In addition, the absence of oxygen within the electricalenergy storage device impedes combustion of the thermal energy absorbingmaterial. For example, phase change materials used as thermal energyabsorbing material are combustible upon changing to a liquid state. Bylimiting oxygen content within the electrical energy storage device,combustion of the phase change material is avoided or reduced.

Typically, venting and combustion of gases from an individual electricalenergy storage cell lasts for only a few seconds. During this timelocalized temperatures can approach temperatures at which adjacentelectrical energy storage cells may become unstable. In order to isolateotherwise stable electrical energy storage cells from thermal energyemanating from a failed cell, the interstices between adjacentelectrical energy storage cells is occupied by the thermal energyabsorbing material described above. The thermal energy absorbingmaterial absorbs thermal energy resulting from failure of the cell andcombustion of gases emanating from the failed cell without an increasein the temperature of the thermal energy absorbing material. The amountof thermal energy that the thermal energy absorbing material presentwithin the electrical energy storage device can absorb before it beginsto increase in temperature depends upon the composition of the thermalenergy absorbing material and the volume of material present. Forexample, a volume of thermal energy absorbing material will besufficient to absorb the entire amount of thermal energy produced byfailure and combustion of a certain number of cells; however, ifadditional cells fail and combust, the thermal energy absorbing materialwill be unable to absorb the additional thermal energy withoutincreasing in temperature.

In the unlikely event failed electrical energy storage cells producethermal energy that exceeds the amount of thermal energy the thermalenergy absorbing material can absorb, the likelihood that additionalelectrical energy storage cells may fail and combust increases,resulting in a potential for self-propagating failure and combustion ofadditional cells. Such self-propagating failure and combustion couldresult in the build-up of pressure within the electrical energy storagedevice to levels that could, in the absence of features included inembodiments described herein, result in uncontrolled bursting of thedevice. Electrical energy storage cell devices of the type describedherein include a burst structure designed to burst at a predeterminedlocation and in a predetermined direction in the event the pressurewithin the device exceeds a threshold amount. Such burst structures aredescribed below in more detail. Such pressure threshold can be set anylevel, provided it is less than the pressure at which the device wouldburst at locations where bursting is not desired. The pressure at whichthe electrical energy storage device bursts may also take intoconsideration the pressure build-up resulting from the failure andcombustion of more than X number of individual cells, where X is thenumber of cells above which failure and combustion of such number ofcells results in the pressure within the device exceeding the pressurenecessary to burst the electrical energy storage device at undesiredlocations. In accordance with embodiments including the burst structuredescribed herein, the device housing will burst and direct hot gases andflames in a direction that reduces the risk of injury to people in thevicinity of the housing.

Referring to FIG. 4, in the embodiment illustrated in FIGS. 1 and 2,base 22 is provided with a burst structure 30. Burst structure 30 inFIG. 4 includes a “scored” feature in the bottom of base 22. Scoring ofthe bottom of base 22 produces scored portions that are thinner than thenon-scored portions of base 22. The scoring is provided by molding thescoring into the base or it can be provided by stamping the scoring intothe base. The scoring can also be provided by other well-understoodtechniques. Although burst structure 30 is illustrated in FIG. 4 ashaving scored portions, it should be understood that features other thana scored feature can be provided as a burst structure. For example, theburst structure can take the form of a pressure relief valve or otherstructure or hardware that will vent the housing 16 when pressure withinthe housing exceeds a predetermined level.

Burst structure 30 is designed to fracture or break open once thepressure within housing 16 reaches a predetermined pressure. Thepredetermined pressure at which the burst structure fractures may be anypressure, for example, a pressure above the pressure that builds upwithin the housing upon the ignition and combustion of a predeterminednumber of individual electrical energy storage cells 14 within housing16. For example, if the number of electrical energy storage cells thatignite and combust is below the predetermined number, the increase inpressure within housing 16 will not be such as to create a significantrisk of uncontrolled bursting of housing 16. On the other hand, if thenumber of electrical energy storage cells that ignite and combust isabove the predetermined number, the increase in pressure within thehousing increases the risk that the housing will burst uncontrollably.Burst structure 30 is designed to fracture or break open once thepressure within housing 16 reaches the predetermined pressure. In theembodiment illustrated in FIG. 4, burst structure 30 is located in thebottom of base 22. Thus, when burst structure 30 bursts, hot combustiongases and flames can exit the bottom of portable electrical energystorage device 10 and be directed downward. Though burst structure 30 isillustrated as being located in the bottom of base 22, it can also belocated elsewhere. For example, burst structure 30 can be located in theside of base 22 or in the side of shell 18 or in the top or side ofcover 20. The specific location of the burst structure will generally beselected so that combustion gases and flames are directed out of housing16 in a safe direction, e.g., away from people that are near housing 16in normal use. In an embodiment where the electrical energy storagedevice is located below the seat of an electrically powered scooter,burst structure 30 is preferably located in the bottom of base 22 suchthat hot gases and flames will exit housing 16 in a direction away fromthe user.

Referring back to FIG. 2, on the side of electrical energy storage cellmodule 12, adjacent base 22, a layer of elastic material 32 separatesthe electrical energy storage cells 14 of electrical energy storage cellmodule 12 from base 22 that includes burst structure 30. At thislocation, a layer of thermal insulating material is omitted becausepropagation of thermal energy and combustion is of less concern becausein the illustrated embodiment, there are no additional electrical energystorage cells below cell module 12 and base 22 is located furthest fromthe user.

Referring to FIG. 3, another embodiment of an electrical energy storagecell device is illustrated and includes more than one electrical energystorage cell module 12. In the embodiment illustrated in FIG. 3, asecond electrical energy storage cell module 34 including a plurality ofindividual electrical energy storage cells 46 is located above firstelectrical energy storage cell module 12 which includes a plurality ofelectrical energy storage cells 14. Positioned above second electricalenergy storage cell module 34 is a second electrical energy storage cellbarrier 36 identical to electrical energy storage cell barrier 24described with reference to FIG. 1. The embodiment of FIG. 3 alsodiffers from the embodiment illustrated in FIG. 1 by including a firstelectrical energy storage cell barrier 38 that includes a layer ofthermal insulating material 40 sandwiched between a layer of elasticmaterial 42 and a layer of elastic material 44. The elastic materials 42and 44 and the thermal insulating material 40 are identical in nature tothe elastic material 32 and thermal insulating material 26 describedabove with reference to FIGS. 1 and 2. The second layer of elasticmaterial 42 of first electrical energy storage cell barrier 38 protectselectrical terminals of the electrical energy storage cells 46 inelectrical energy storage cell module 34.

Unlike the embodiment illustrated and described with reference to FIGS.1 and 2, the embodiment of an electrical energy storage deviceillustrated in FIG. 3 includes a second electrical energy storage cellmodule 34 above electrical energy storage cell module 12. The provisionof a second electrical energy storage cell module 34 renders itdesirable to protect electrical energy storage cell module 34 fromcombustion that may occur within first electrical energy storage cellmodule 12 and vice versa. This protection is provided by the three-layerelectrical energy storage cell barrier 38.

It should be understood that although embodiments including a singleelectrical energy storage cell module and two electrical energy storagecell modules have been described above with reference to FIGS. 1-3, inaccordance with the subject matter described herein, more than twoelectrical energy storage cell modules can be provided. When more thantwo electrical energy storage cell modules are provided, in accordancewith embodiments described herein, a three layer electrical energystorage cell barrier similar to electrical energy storage cell barrier38 in FIG. 3 is provided between electrical energy storage cell modules.

In addition, although specific embodiments of electrical energy storagecell barriers 24, 36 and 38 have been described, it should be understoodthat additional layers of thermal insulating material can be provided ifadditional thermal insulation is desired. Similarly, additional layersof elastic material can be provided if further protection of electricterminals is desired.

FIG. 5 illustrates schematically several different paths gases andthermal energy emanating from a failed electrical energy storage cellwithin second electrical energy storage cell module 100 may take throughthe thermal absorbing material. In the first instance schematicallyrepresented by dotted line 102, gases and thermal energy emanating froman upper end of an electrical energy storage cell (not shown) making upa portion of first electrical energy storage cell module 100 impingeupon the inner surface of a top cover 104 of second electrical energystorage cell module 100, are reflected by the inner surface of top cover104 and are contained within second electrical energy storage cellmodule 100. The deflection of these gases and thermal energy towards theinterior of the second electrical energy storage cell module isundesirable for at least the reasons that the gases and thermal energymay cause damage to otherwise undamaged electrical energy storage cellswithin electrical energy storage cell module 100. For example, thethermal energy from combustion of the gases may cause otherwiseundamaged electrical energy storage cells to self-ignite which couldpropagate a thermal runaway of the electrical energy storage cell module100. In addition, combustion of the gases within second electricalenergy storage cell module 100 may result in an increase in pressurewithin second electrical energy storage cell module 100. If suchpressure buildup exceeds the burst pressure of second electrical energystorage cell module 100, second electrical energy storage cell module100 may burst, possibly with explosive force.

In another instance, represented schematically by dotted line 106, thegases and thermal energy pass through cover 104 and escape secondelectrical energy storage cell module 100. The gases and thermal energyflow around first electrical energy storage cell module 108. While thisinstance may have a reduced likelihood that the gases and thermal energycause electrical energy storage cells within second electrical energystorage cell module 100 to fail, rupture, or ignite, or that secondelectrical energy storage cell module 100 will burst, there is anincreased risk that the gases and thermal energy traveling along dottedline 106 may cause electrical energy storage cells within firstelectrical energy storage cell module 108 to fail, rupture or ignitewhich could lead to an increased risk that portable electrical energystorage device 120 will burst. Ignition of electrical energy storagecells in first electrical energy storage cell module 108 could occurwhen localized temperatures within first electrical energy storage cellmodule rise above temperatures at which failure and/or ignition ofindividual portable electrical energy storage cells occurs. For example,gases and thermal energy emanating from electrical storage cell module100 will impinge upon the underside of first electrical energy storagecell module 108 and could cause localized temperatures within firstelectrical energy storage cell module 108 to rise above temperatures atwhich individual electrical energy storage cells within electricalenergy storage cell module 108 ignite and/or rupture. Gases and thermalenergy that impinge upon the underside of first electrical energystorage cell module 108 may dissipate and move to the periphery of firstelectrical energy storage cell module 108 where they may pass betweenelectrical energy storage cell module 108 and shell 110 of theillustrated portable electrical energy storage device 120. Gases andthermal energy present in this location could cause localizedtemperatures within first electrical energy storage cell module 108 toexceed temperatures at which individual electrical energy storage cellswithin electrical energy storage cell module 108 fail, rupture and/orignite.

Referring to FIG. 6, an exploded view of an electrical energy storagedevice in accordance with non-limiting embodiments described hereinincludes an electrical energy storage cell module 200. Electrical energystorage cell module 200 is illustrated schematically; however, it isunderstood that module 200 includes a plurality of individual electricalenergy storage cells similar to those illustrated in FIGS. 2 and 3. Inaddition, electrical energy storage cell module 200 is illustratedschematically as a rectangular module; however, electrical energystorage cell module 200 is not limited to rectangular shapes and maytake other shapes such as a cylinder or a rectangular shape with roundedcorners. Though not illustrated, module 200 includes electricalconnections to electrically connect individual electrical energy storagecells within module 200 and connections to electrically connect module200 to devices powered by module 200. Module 200 includes an outer wall202 defining a periphery of module 200.

Positioned adjacent the four sides of outer wall 202 are a pair ofmodule sidewalls 204. Each module sidewall 204 includes an inner surface205 which faces electrical energy storage cell module 200 and an outersurface 208 on the side of module sidewall 204 opposite inner surface205. In the illustrated embodiment, outer surface 208 faces away fromelectrical energy storage cell module 200. In non-limiting embodimentsof FIG. 6, module sidewall 204 is illustrated as being two parts thatare mirror images of each other. It should be understood that modulesidewalls 204 can be comprised of a single part which slides onto module200 or can be comprised of more than two parts. Module sidewall 204includes a plurality of vents 206 passing through module sidewall 204from its inner surface 205 to its outer surface 208. In the illustratedembodiment, vents 206 are shown being round and aligned in a pluralityof vertical columns. Vents 206 are not limited to being round and can beother shapes, such as oval or rectangular. In addition, vents 206 neednot be provided in a plurality of vertical columns and can be arrangedin different formations other than vertical columns. Vents 206 arelocated in module sidewall 204 at locations which correspond to voidspaces within electrical energy storage cell module 200. Such voidspaces occur between individual electrical energy storage cells withincell module 200. By aligning vents 206 with such void spaces, flow offluids that promote convective or other types of heat transfer betweenindividual electrical energy storage cells and the fluid and one side ofmodule sidewall 204 and an opposite side of module sidewall 204 can morereadily occur, e.g., during normal operation. Though not illustrated, incertain embodiments, module sidewall 204 can be shaped so that itmatches the contour of the outer side of electrical energy storage cellmodule 200 resulting from the placement of individual electrical energystorage cells at the periphery of electrical energy storage cell module200. Materials used for sidewall 204 are of the type that can withstandhigh temperatures associated with gases and thermal energy that aregenerated upon failure of an electrical energy storage cell. Suchtemperatures can be in the range of 1000° C. or higher. Exemplarymaterials for sidewall 204 include metals or plastics or other materialscapable of withstanding such high temperatures without combusting ordistorting significantly.

Located above electrical energy storage cell module 200 is an electricalenergy storage cell barrier 210. Electrical energy storage cell barrier210 serves several functions, including serving as a barrier to thespread of combustion from electrical energy storage cell module 200 toanother electrical energy storage cell module, serving to electricallyisolate electrodes of the electrical energy storage cells withinelectrical energy storage cell module 200 from electrically conductivecomponents of the electrical storage cell barrier 210, providing abarrier to heat transfer from or to electrical energy storage cellmodule 200 and protecting electrodes of electrical energy storage cellswithin electrical energy storage cell module 200 from damage caused bycontact with rigid or abrasive materials of electrical energy storagecell barrier 210. In non-limiting embodiments of FIG. 6, electricalenergy storage cell barrier 210 includes an electrical isolation layer212 of a dielectric material sandwiched between an electrical energystorage cell contact protection layer 214 of an elastic material and acombustion barrier layer 216 of a non-combustible material.

Electrical energy storage cell contact protection layer 214 is anelastic material, non-limiting examples of which include elasticmaterials that are noncombustible at temperatures of about 130° C. andhigher. The phrase “elastic material” refers to materials that areflexible, resilient and capable of substantially returning to theiroriginal shape after deformation. Elastic materials of the typedescribed herein are not limited to flexible and resilient materialsthat return fully to their original shape after being deformed. Elasticmaterials in accordance with non-limiting examples described hereininclude materials that are flexible and resilient and which after beingdeformed do not return fully to their original shape. In non-limitingembodiments, electrical energy storage cell contact protection layer 214provides physical protection to terminals of electrical energy storagecells making up a portion of electrical energy storage cell module 200by being formed from a material that is softer than the material makingup the electrical energy storage cell terminals. In yet othernon-limiting examples, the elastic material of the electrical energystorage cell contact protection layer 214 is electrically nonconductive.The electrically nonconductive property of electrical energy storagecell contact protection layer 214 prevents electrical energy storagecell contact protection layer 214 from adversely affecting, e.g.,short-circuiting, the terminals or conductive features electricallyconnected to the electrical energy storage cells. Non-limiting examplesof materials from which electrical energy storage cell protection layer214 is formed include elastic materials that have a hardness of lessthan about 50 to 100 on a Shore scale and an electrical resistivity ofgreater than about 10 to about 20 ohms or more. In specific embodiments,the elastic material is a fluoropolymer rubber, butyl rubber,chlorosulfonated polyethylene rubber, epichlorohydrin rubber, ethylenepropylene rubber, fluoroelastomer rubber, fluorosilicone rubber,hydrogenated nitrile rubber, natural rubber, nitrile rubber,perfluoroelastomer rubber, polyacrylic rubber, polychloroprene rubber,polyurethane rubber, silicone rubber and styrene butadiene rubber. Inother specific embodiments, the elastic material is a low modulus,conformable foam, such as a thermoset closed-cell polyurethane foam orother closed cell thermoset polymer.

Electrical energy storage cell contact protection layer 214 also servesas a barrier or impediment to propagation of combustion from one side ofelectrical energy storage cell contact protection layer 214 to anopposite side of electrical energy storage cell contact protection layer214. Electrical energy storage cell contact protection layer 214 servesas a barrier or impediment to propagation of combustion by providing anon-combustible impediment or fire block to flames resulting fromcombustion of gases emanating from a failed electrical energy storagecell within electrical energy storage cell module 200. In yet otherembodiments, electrical energy storage cell contact protection layer 214provides thermal insulation between electrical energy storage cellmodule 200 and electrical isolation layer 212. Such thermal insulationimpedes and/or acts as a barrier to transfer of thermal energy fromelectrical energy storage cell module 200 to electrical isolation layer212. Impeding thermal transfer between electrical energy storage cellmodule 200 and electrical isolation layer 212 shields adjacentelectrical energy storage cells (not shown) of an adjacent electricalenergy storage cell module (not shown) located above electrical energystorage cell module 200 from thermal energy that could result in failureof the electrical energy storage cells in the adjacent electrical energystorage cell module. For example, in the rare event that an electricalenergy storage cell of electrical energy storage cell module 200 fails,the storage cell emits gases which upon combustion will generate largeamounts of thermal energy. This thermal energy could cause otherelectrical energy storage cells to fail and potentially emit combustiblegases. If these gases ignite a thermal run-away of the electrical energystorage cells could occur. Non-limiting examples of materials for use inelectrical energy storage cell contact protection layer 214 have thermalconductivity values that are less than about 0.5 BTU/ft²/hr/inch attemperatures corresponding to temperatures at which the electricalenergy storage cells emit combustible gases and ignition of those gasesoccurs. According to some embodiments illustrated in FIGS. 6 and 7,electrical energy storage cell contact protection layer 214 is about 0.1mm to 3.0 mm thick. In other embodiments, electrical energy storage cellcontact protection layer 214 is about 0.5 mm to 2.0 mm thick, and in yetother embodiments, electrical energy storage cell contact protectionlayer 214 is about 0.75 mm to 1.25 mm thick. Electrical energy storagecell contact protection layer 214 may be thicker or thinner than thedescribed non-limiting ranges, depending on, among other things, theamount of combustion migration inhibition, thermal insulation,electrical energy storage cell terminal protection and/or shockabsorption desired.

Electrical isolation layer 212 is formed from an electricallynonconductive material, non-limiting examples of which include materialsthat are noncombustible at temperatures of about 130° C. and higher andexhibit dielectric constants which make them electrical insulators. Innon-limiting embodiments, electrically nonconductive materials of theelectrical isolation layer 212 prevent electrical isolation layer 212from adversely affecting, e.g., short-circuiting, the terminals orconductive features electrically connected to the electrical energystorage cells. The electrically nonconductive materials of theelectrical isolation layer 212 also electrically isolate terminals ofelectrical energy storage cells and electrical circuits making upelectrical energy storage cell module 200 from combustion barrier layer216. In yet other non-limiting embodiments, electrically nonconductivematerial making up electrical isolation layer 212 is noncombustible orflame retardant, thus allowing electrical isolation layer 212 to impedeor prevent propagation of combustion from one side of electricalisolation layer 212 to an opposite side of electrical isolation layer212. In other non-limiting embodiments, the electrically nonconductivematerial making up electrical isolation layer 212 provides thermalinsulation between electrical energy storage cell contact protectionlayer 214 and combustion barrier layer 216. Such thermal insulationimpedes and/or acts as a barrier to transfer of thermal energy fromelectrical energy storage cell module 200 via electrical energy storagecell contact protection layer 214 to electrical isolation layer 212.Impeding thermal transfer between electrical energy storage cell module200 and combustion barrier layer 216 helps to protect adjacentelectrical energy storage cell modules (not shown) from thermal energythat could result in failure of electrical energy storage cells in theadjacent electrical energy storage cell modules. For example, in therare event an electrical energy storage cell of electrical energystorage cell module 200 fails and emits gases, which upon combustionwill generate significant amounts of thermal energy, this thermal energycould cause other electrical energy storage cells in adjacent electricalenergy storage cell modules to fail, rupture and self-ignite.Non-limiting examples of materials for use in electrical isolation layer212 have thermal conductivity values that are less than about 3BTU/ft²/hr/inch, less than about 2 BTU/ft²/hr/inch and less than about 1BTU/ft²/hr/inch at temperatures corresponding to temperatures where theelectrical energy storage cells rupture and emit combustible gases whichmay ignite. In some embodiments, the electrically nonconductive materialof the electrical isolation layer 212 is self-extinguishing.

The electrically nonconductive material may include ceramic materials,vermiculite-based materials or other materials known to benon-electrically conductive or a poor conductor of electricity and agood thermal insulator. The carrier for the ceramic materials may bepaper-based, ceramic impregnated cloths, fiberglass or other materialscapable of being formed into thin sheets. Non-limiting examples ofelectrically nonconductive materials include materials comprisingceramic fibers, such as a compressible fiber sheet made from a weave ofsilica and calcium oxide fibers held together with a noncombustibleorganic binder. Such ceramic fibers can be formed from alumina, mullite,silicon carbide, zirconia or carbon. In specific embodiments, theelectrically nonconductive material includes silica/silica fibers,aluminum, Kevlar®, Nomex®, and calcium-magnesium-silicate fibers. Thoughnot intending to be limited to such, some electrically nonconductivematerials for use in electrical isolation layer 212 are fire resistantto 1260° C. or higher. According to non-limiting embodiments illustratedin FIGS. 6 and 7, the layer of electrically nonconductive materialmaking up electrical isolation layer 212 has a thickness ranging fromabout 0.1 mm to about 3 mm. In other embodiments, electrical isolationlayer 212 is about 0.25 mm to 2.0 mm thick, and in yet otherembodiments, electrical isolation layer 212 is about 0.35 mm to 1.25 mmthick. Electrical isolation layer 212 may be thicker or thinner than thedescribed non-limiting ranges, depending on, among other things, theamount of electrical isolation, combustion migration inhibition, and/orthermal insulation desired.

Combustion barrier layer 216 is a non-combustible, high strengthmaterial, non-limiting examples of which include materials that arenoncombustible at temperatures of about 130° C. and higher and are ableto withstand the types of forces imparted and conditions created bygases emanating from a failed electrical energy storage cell ofelectrical energy storage cell module 200. Failure of an electricalenergy storage cell, e.g., due to structural damage and/orshort-circuiting, can result in the rupture of the failed electricalenergy storage cell as a result of pressure build up within the cell.Upon rupture, the gases within the electrical energy storage cell mayescape at high velocities and combust. The noncombustible, high-strengthmaterial of combustion barrier layer 216 is selected from materials thatcan withstand the forces caused by these gases escaping the portableelectrical energy storage device at high velocities and withstand thehigh temperatures associated with combustion of such gases. Combustionbarrier layer 216 impedes and ideally prevents hot gases emanating froma failed electrical energy storage cell and/or flames resulting fromcombustion of such hot gases from impinging upon an adjacent electricalenergy storage cell module above electrical energy storage cell module200. Impeding and/or preventing gases and/or flames from impinging uponan adjacent electrical energy storage cell module reduces the likelihoodthat electrical energy storage cells in the adjacent electrical energystorage cell module will fail due to exposure to the temperaturesproduced when the gases from a failed electrical energy storage cellcombust. In non-limiting embodiments, the noncombustible, high-strengthmaterial of combustion barrier layer 216 acts as an impediment orbarrier to propagation of combustion from electrical energy storage cellmodule 200 to adjacent electrical energy storage cell modules.Non-limiting examples of materials for use as combustion barrier layer216 include metals or metal alloys that can withstand temperatures ofabout 130° C. or higher without melting. In other non-limiting examples,materials for use as combustion barrier layer 216 include metals that donot melt at temperatures of about 500° C. or higher, 750° C. or higher,or even more than 1000° C. In other embodiments, the metals making upcombustion barrier layer 216 do not melt after being exposed totemperatures of more than about 1000° C. for at least 10 seconds. In yetother embodiments, materials for use as combustion layer 216 includemetals that do not melt after being exposed to temperatures of about1400° C. for a period of at least 1 second. In specific non-limitingembodiments, combustion barrier layer 216 is formed from copper, acopper alloy, nickel, or a nickel alloy. While copper, copper alloy,nickel and nickel alloy have been described as exemplary metals fromwhich combustion barrier layer 216 may be formed, combustion barrierlayer 216 can be formed from other metals or non-metallic materialscapable of impeding or preventing the gases and/or flames fromcombustion of the gasses from impinging upon an adjacent electricalenergy storage cell module.

Located below electrical energy storage cell module 200 is a secondelectrical energy storage cell barrier 218. Electrical energy storagecell barrier 218 includes an electrical energy storage cell contactprotection layer 220, electrical isolation layer 222 and a combustionbarrier layer 224. The description with regard to electrical energystorage cell barrier 210 and its electrical energy storage cell contactprotection layer 214, electrical isolation layer to 212, and combustionbarrier layer 216 applied equally to the electrical energy storage cellcontact protection layer 220, electrical isolation layer 222 andcombustion barrier layer 224 of electrical energy storage cell barrier218. That description is not repeated in the interest of brevity. Secondelectrical energy storage cell barrier 218 differs in the orientation ofits electrical energy storage cell contact protection layer 220,electrical isolation layer 222 and combustion barrier layer 224. Thesethree layers of electrical energy storage cell barrier 218 are a mirrorimage of the same three layers of electrical energy storage cell barrier210. In other words, moving away from electrical energy storage cellmodule 200 in FIG. 6 places electrical energy storage cell contactprotection layer 220 closest to electrical energy storage cell module200. Located below electrical energy storage cell contact protectionlayer 220 is electrical isolation layer 222 and below electricalisolation layer 222 is combustion barrier layer 224.

Though not illustrated in FIG. 6, electrical energy storage device 120as further illustrated in FIG. 7 includes at least one additionalelectrical energy storage cell module 226 located below electricalenergy storage cell module 200 illustrated in FIG. 6. Both electricalenergy storage cell module 200 and electrical energy storage cell module226 include a plurality of electrical energy storage cells 232. In otherembodiments, electrical energy storage device 120 may include more thantwo electrical energy storage cell modules. For example, electricalenergy storage device 120 may include three or more electrical energystorage cell modules. In FIG. 7, electrical energy storage cell module226 is sandwiched between electrical energy storage cell barrier 228 andelectrical energy storage cell barrier 230. Electrical energy storagecell barrier 228 is identical to electrical energy storage cell barrier210 and electrical energy storage cell barrier 230 is identical toelectrical energy storage cell barrier 218. Accordingly, descriptions ofelectrical energy storage cell barrier 228 and electrical energy storagecell barrier 230 are omitted in the interest of brevity.

Referring to FIG. 7, electrical energy storage cell module 200 is spacedapart from electrical energy storage cell module 226 by a distance D. Innon-limiting embodiments, distance D ranges from about 5 mm to about 20mm, in other non-limiting embodiments, distance D ranges from about 7 mmto about 15 mm and in yet other embodiments, distance D ranges fromabout 8 mm to about 11 mm. In the illustrated embodiment of FIGS. 6 and7, four spacers 234 are positioned between electrical energy storagecell module 200 and electrical energy storage cell module 226. Spacers234 are cylindrical in shape and each includes a central bore. Thecentral bore of each spacer 234 is in fluid communication with openings236 through each of electrical energy storage cell contact protectinglayers 214 and 220, electrical isolation layers 212 and 222 andcombustion barrier layer 216 and 224. The combination of the centralbore for spacers 234 and the openings 236 places the interior ofelectrical energy storage cell module 200 in fluid communication withthe interior of electrical energy storage cell module 226. This fluidcommunication allows pressure within electrical energy storage cellmodules 200 and 226 to equalize.

In specific embodiments of the subject matter described herein, interiorsurface 205 of module sidewall 204 carries a fireproof or fire-resistantmaterial, such as an intumescent paint. Alternatively, such fireproof orfire-resistant material may be carried by the exterior outer wall 202 ofelectrical energy storage cell module 200 between the exterior surfaceof such module and the interior surface of module sidewall 204.Providing such a fireproof/fire-resistant material impedes migration offlames on the exterior of module sidewall 204 into the interior ofelectrical energy storage cell module 200.

As described above with reference to FIG. 6, individual electricalenergy storage cell modules 100 or 108 in FIG. 5 may include sidewalls204 that include vents 206 passing through sidewalls 204. In suchembodiments, gases and thermal energy emanating from an electricalenergy storage cell (not shown) making up a portion of electrical energystorage cell module 100 in FIG. 5 may escape module 100 through vents206 in sidewalls 204.

The present inventors have observed that in certain embodiments, thethermal energy absorbing material within the electrical energy storagedevice impedes flow, within the electrical energy storage device, ofgases generated when an electrical energy storage cell fails. Withoutintending to be bound by any particular theory, it is believed that thisimpediment arises as a result of at least a portion of the thermalenergy absorbing material being in a solid-state within a sealed vesselwhen gases are produced by a failed electrical energy storage cell. Incertain embodiments described herein, sacrificial members are providedin the thermal energy absorbing material, whereupon thermaldecomposition of the sacrificial members, channels in the thermal energyabsorbing material remain. These channels provide pathways for fluids,such as gases generated when an electrical energy storage cell fails, toflow.

Referring to FIGS. 5 and 7, a sacrificial member 302 is located belowelectrical energy storage cell module 100. Another sacrificial member304 is located between electrical energy storage cell module 100 andelectrical energy storage cell module 108. In FIGS. 5 and 7, asacrificial member is not illustrated above electrical energy storagecell module 108; however, a sacrificial member could be provided aboveelectrical energy storage cell module 108. Additional sacrificialmembers 306 and 310 are provided between sidewalls 308 of shell 110 andboth electrical energy storage cell modules 100 and 108. As describedbelow in more detail, these sacrificial members are formed from amaterial that thermally decomposes. Upon thermal decomposition of thesacrificial members, a void or channel in the thermal energy absorbingmaterial is formed in the space occupied by the sacrificial member priorto decomposition. Fluids, e.g., gases resulting from the failure of anelectrical energy storage cell, can flow within these channels withoutbeing blocked by the thermal energy absorbing materials.

Referring to FIG. 6, exemplary embodiments of sacrificial members 302and 304 in FIG. 5 are illustrated. As shown in FIG. 6, sacrificialmembers 302 and 304 are rectangular in shape, similar to the shape andsize of electrical energy storage cell contact protection layer 214,electrical isolation layer 212 and combustion barrier layer 216. Itshould be understood that the particular shape and size of sacrificialmembers 302 and 304 is not limited to those illustrated in FIG. 6 andthat sacrificial members 302 and 304 can take different shapes and be ofdifferent sizes. The shape and sizes of sacrificial members 302 and 304may be dictated by the shape of shell 110 and/or modules 100 and 108.FIG. 6 also illustrates exemplary embodiments of additional sacrificialmembers 306 and 310 in FIG. 5. As shown in FIG. 6, sacrificial members306 and 310 are rectangular in shape, extending from the bottom ofelectrical energy storage cell module 100 to approximately the top ofelectrical energy storage cell module 108. It should be understood thata particular shape and size of additional sacrificial members 306 and310 are not limited to those illustrated in FIG. 6 and that sacrificialmembers 306 and 310 can take different shapes and be of different sizes,again both of which may be dictated by the shape of shell 110 and/ormodules 100 and 108. In addition, sacrificial members 306 and 310 can belocated adjacent additional or different sides of electrical energystorage cell modules 100 and 108 or fewer sides of electrical energystorage cell modules 100 and 108.

The sacrificial members are formed from a material that does notthermally decompose when exposed to an environment below a firsttemperature and does thermally decompose when exposed to an environmentat a second temperature that is greater than the first temperature. Inaddition, the material from which the sacrificial members are formedpreferably does not significantly reduce the thermal absorption capacityof the thermal absorbing material. The material from which thesacrificial members are formed should be capable of substantiallyretaining its shape after coming into contact with the thermal energyabsorbing material when the thermal energy absorbing material is in afluid state or a solid state.

The material from which the sacrificial members are formed does notthermally decompose when exposed to environments at temperaturesexperienced within the electrical energy storage device under normaloperating conditions; however, the material will thermally decomposewhen exposed to an environment experienced within the electrical energystorage device when one or more electrical energy storage cells fails.Thermal decomposition refers to a reduction in the volume of thematerial, from which the sacrificial member is formed, that occurs whenthe temperature of the environment containing the material increasesabove a decomposition temperature of the material. Thermal decompositioncan be the result of shrinkage, combustion, melting, vaporization,freezing, condensation, sublimation, or any other phenomena that resultsin a reduction in the volume of the material due to the temperature ofthe environment containing the material increasing above thedecomposition temperature of the material.

Exemplary materials for use as sacrificial members include materialsthat thermally decompose when exposed to an environment at temperaturesgreater than or equal to about 50° C. but do not thermally decomposewhen exposed to an environment at temperatures less than about 50° C.,materials that thermally decompose when exposed to an environment attemperatures greater than or equal to about 60° C. but do not thermallydecompose when exposed to an environment at temperatures less than about60° C. and materials that thermally decompose when exposed to anenvironment at temperatures greater than or equal to about 70° C. but donot thermally decompose when exposed to an environment at temperaturesless than about 70° C. Exemplary materials for use as sacrificialmembers can include materials that when thermally decomposed have avolume that is at least 25% less than the volume of the material beforethermal decomposition, at least 50% less than the volume of the materialbefore thermal decomposition, at least about 100% less than the volumeof the material before thermal decomposition or at least about 200% lessthan the volume of the material before thermal decomposition. Exemplarymaterials for use in forming sacrificial members also include materialsthat when thermally decomposed have a volume that is more than about200% less than the volume of the material before thermal decomposition.Materials which after thermal decomposition have a volume that is not atleast 25% less than the material before thermal decomposition may alsobe used to form sacrificial members; however, upon thermaldecomposition, such materials will result in smaller voids within thethermal absorbing material through which fluids may flow.

Exemplary materials from which sacrificial members may be formed inaccordance with embodiments described herein include polymericmaterials. Non-limiting examples of polymeric materials for use informing sacrificial members include polystyrene, styrene copolymers,polypropylene and propylene copolymers and blends of these polymericmaterials with other polymeric and/or non-polymeric materials. Thepolymeric materials can be either in a solid form or a foamed form.Solid forms can be produced using injection molding, vacuum forming orextrusions techniques. Foamed forms include expanded closed cell foamsand extruded closed cell foams.

Referring to FIG. 6, electrical isolation layer 212 includes a pluralityof biased vents 238. Combustion barrier layer 216 includes a pluralityof biased vents 240. Electrical isolation layer 222 includes a pluralityof biased vents 242 and combustion barrier layer 224 includes aplurality of biased vents 244. Biased vents 238, 240, 242 and 244 areessentially identical. In embodiments described with reference to FIG.6, biased vents 238 and 240 open in an upward direction while biasedvents 242 and 244 open in a downward direction. Biased vents 238, 240,242 and 244 are essentially aligned with individual electrical energystorage cells 232 making up electrical energy storage cell module 200.

The following description of biased vents 240 applies equally to biasedvents 238. Referring additionally to FIGS. 8 and 9, biased vents 240include at least one flap 248 formed in combustion barrier layer 216. Inthe exemplary embodiment of FIGS. 8 and 9, flap 248 has a square shape.Flap 248 is defined by a plurality of scored portions 250, 252 and 254which pass through combustion barrier layer 216. Scored portions 250,252 and 254 can be formed using cutting devices suitable for cuttingmetal such as blades, stamps, lasers, and the like. Scored portions 250,252 and 254 defined three sides of square flap 248. The remaining sideis defined by a hinge portion 256. Hinge portion 256 does not passcompletely through combustion barrier layer 216 and serves as ahinge-like structure along which flap 248 bends so flap 248 can movefrom a closed position shown in FIG. 8 to an open position asillustrated in FIG. 9. Hinge portion 256 can be formed using devicescapable of compressing combustion barrier layer 216 at the location ofhinge portion 256. While hinge portion 256 is illustrated and describedas a crimped structure, embodiments described herein are not limited toa hinge portion 256 that is crimped and include other structures thatcan function as a hinge for flap 248. For example, hinge portion 256 canbe provided by perforations or other structure that facilitates foldingor bending of combustion barrier layer 216 along hinge portion 256.Hinge portion 256 of flap 248 can be designed so that when apredetermined threshold pressure is exerted on flap 248, biased vent 238bends along its hinge portion and opens in the manner illustrated inFIG. 9.

In addition to biased vents 240 provided in combustion barrier layer216, similar biased vents 238 are provided in electrical isolation layer212. In the exemplary embodiments illustrated in FIGS. 6, 8 and 9,biased vents 240 and biased vents 238 are substantially identical;however, embodiments described herein are not limited to portableelectrical energy storage devices that include biased vents 240 andbiased vents 238 that are substantially identical. Referring to FIG. 9,biased vents 238 provided in electrical isolation layer 212 are formedby three scored portions and a hinge portion. In the illustratedembodiments, the three scored portions of biased vents 238 underlie thescored portions 250, 252 and 254 of biased vents 240, the hinge portionof biased vents 238 underlie the hinge portion 256 of biased vents 240and flap 239 of biased vent 238 underlies flap 248. In otherembodiments, a scored portion of biased vents 238 underlies hingeportion 256 of biased vents 240. In certain embodiments, the peripheraldimensions of flap 239 may be slightly less than the peripheraldimensions of flap 248. This difference in peripheral dimensions betweenflap 239 and flap 248 allows flap 239 to pass through the opening incombustion barrier layer 216 when flap 248 is open. Conversely, thesmaller peripheral dimensions of flap 239 compared to flap 248 impedespassing of flap 248 through the opening of biased vent 238. In addition,the hinge portion of biased vents 238 maybe laterally offset slightlyfrom hinge portions 256 of biased vents 240 to promote freer opening ofbiased vent 238 through the opening in combustion barrier layer 216.

The underside 258 of the flap of biased vents 238 contacts the uppersurface of electrical energy storage cell contact protection layer 214.This contact impedes movement of the flap in a downward direction inFIGS. 8 and 9 which in turn impedes movement of flap 248 in a downwarddirection. In contrast, flaps 239 and flaps 248 are able to move in anupward direction as illustrated in FIG. 9. Thusly, biased vents 238 andbiased vents 240 are “one-way” vents capable of opening in a directionaway from electrical energy storage cell module 200, but not in adirection toward electrical energy storage cell module 200. Biased vents238 and 240 are biased to a closed position illustrated in FIG. 8,however, a buildup of pressure within electrical energy storage cellmodule 200, or the force of gases emitted from a failed electricalenergy storage cell, can provide a driving force causing flaps 239 and248 to bend along their respective hinge portions and open in an upwarddirection. In addition to allowing gas within electrical energy storagecell module 200 to escape, the one-way characteristic of the biasedvents also impedes or prevents gases that may impinge on the biasedvents from coming in direct contact with an electrical energy storagecell making up an electrical energy storage cell module that is on aside of the biased vents opposite from the side upon which the gasesimpinge. Because the biased vents open outward, and not inward, from anelectrical energy storage cell module. the biased vents allow exhaust ofgases and thermal energy emanating from a failed electrical energystorage cell in the electrical energy storage cell module and preventgases and thermal energy impinging upon biased vents of an adjacentelectrical energy storage cell module from coming in direct contact withelectrical energy storage cells of the adjacent electrical energystorage cell module.

Electrical isolation layer 222 includes a plurality of biased vents 242and combustion barrier layer 224 includes a plurality of biased vents244. The description above of biased vents 238 and biased vents 240 andthe features making up biased vents 238 and 240 applies equally tobiased vents 242 and biased vents 244, respectively, with the exceptionthat biased vents 242 and 244 open in a downward direction withreference to the non-limiting embodiment illustrated in FIG. 6.

Referring to FIG. 7, when pressure within second electrical energystorage cell module 226 exceeds the pressure at which biased vents 238and 240 (in FIG. 6) open, biased vents 238 and 240 open allowing gas toescape through the biased vents. Allowing the gas to escape secondelectrical energy storage cell module 226 reduces the risk that module226 will burst. The escaping gas may follow a path similar to dottedline 106 in FIG. 6. The gas and thermal energy escaping from secondelectrical energy storage cell module 226 impinges upon the underside offirst electrical energy storage cell module 200 where it is dissipatedalong the underside of first electrical energy storage cell module 200,finding its way to the periphery of first electrical energy storage cellmodule 200 and the space between first electrical energy storage cellmodule 200 and shell 282. As the gas and thermal energy pass through thespace between first electrical energy storage cell module 200 and shell282, it dissipates the thermal energy of the gas or combusting gas. InFIG. 7, second electrical energy storage cell module 226 is spaced apartfrom first electrical energy storage cell module 200 by a distance D.Spacing of second electrical energy storage cell module 226 from firstelectrical energy storage cell module 200 by the distance D promotesdissipation of the gases and thermal energy emanating from secondelectrical energy storage cell module 226 by allowing the gas andthermal energy to spread out laterally across a larger surface area.Promoting the dissipation of the thermal energy of the gases emanatingfrom the second electrical energy storage module over a larger surfacearea reduces the magnitude of thermal energy focused on a small area ofelectrical energy storage cell module 200, thereby reducing thelikelihood that such focused thermal energy will cause failure orexplosion of an electrical energy storage cell 232 in first electricalenergy storage cell module 200. Opening of biased vents 238 and 240reduces the likelihood that gases and thermal energy emanating from afailed electrical energy storage cell 232 in second electrical energystorage cell module 226 will be directed internally within secondelectrical energy storage cell module 226, e.g., along dotted line 102in FIG. 5.

As gas and thermal energy flows between first electrical energy storagecell module 200 and shell 282, first electrical energy storage cellmodule 200 is at least fully or partially separated from the gases andthermal energy by module sidewalls 204. Pressure differentials acrossmodule sidewalls 204 are mitigated by vents 206 in module sidewalls 204.Vents 206 also facilitate equalization of pressure within the portableelectrical energy storage device 120 by allowing pressure on one side ofmodule sidewalls 204 to equilibrate with pressure on the other side ofmodule sidewalls 204. Equalization of pressure within the portableelectrical energy storage device 120 is also promoted by openings 236 inelectrical energy storage cell barrier 210 and electrical energy storagecell barrier 218. Openings 236 permit gases within first electricalenergy storage cell module 200 to pass through electrical energy storagecell barrier 210 or electrical energy storage cell barrier 218 into theinterior space of portable electrical energy storage device 120 or intoadjacent electrical energy storage cell module 226. Passing of gasthrough electrical energy storage cell barrier 210 and electrical energystorage cell barrier 218 serves to equalize pressure within electricalenergy storage cell module 200 and the pressure outside electricalenergy storage cell module 200 within shell 282 or the pressure withinelectrical energy storage cell module 226. In certain embodiments, tubesor pipe may extend between openings 236 located above an electricalenergy storage cell module and openings 236 located below the electricalenergy storage cell module.

While the operation and advantages of biased vents in accordance withnonlimiting embodiments described herein have been described withreference to the biased vents in electrical energy storage cell barrier210, the same operation and advantages are provided by biased vents 242and 244 and electrical energy storage cell barrier 218. Although onlytwo electrical energy storage cell modules 200 and 226 are illustratedin the nonlimiting embodiments of FIGS. 5 and 7, portable electricalenergy storage devices in accordance with embodiments described hereininclude those that contain more than two electrical energy storage cellmodules of the type described herein.

The foregoing detailed description has set forth various embodiments ofthe devices via the use of schematic illustrations and examples. Insofaras such schematics and examples contain one or more functions and/oroperations, it will be understood by those skilled in the art that eachfunction and/or operation within such structures and examples can beimplemented, individually and/or collectively, by a wide range ofhardware and combinations thereof. The various embodiments describedabove can be combined to provide further embodiments. All of the U.S.patents, U.S. patent application publications, U.S. patent applications,foreign patents, foreign patent applications and non-patent publicationsreferred to in this specification and/or listed in the Application DataSheet are incorporated herein by reference, in their entirety. Aspectsof the embodiments can be modified, if necessary to employ concepts ofthe various patents, applications and publications to provide yetfurther embodiments.

While generally discussed in the environment and context of powersystems for use with personal transportation vehicles such asall-electric scooters and/or motorbikes, the teachings herein can beapplied in a wide variety of other environments, including othervehicular as well as non-vehicular environments. Further, whileillustrated with reference to specific shapes and orientations, theillustrations and descriptions are not intended to be exhaustive or tolimit the embodiments to the precise forms illustrated. For example,electrical energy storage cells need not be round cylinders, but couldtake different shapes such as square cylinders, square boxes orrectangular boxes. Similarly, embodiments utilizing multiple electricalenergy storage cell modules have been illustrated and described withreference to the modules being stacked one above the other; however,such descriptions are not intended to be exhaustive or to limit theembodiments described herein to such precise configurations. Forexample, electrical energy storage cell modules may be placed side byside and separated by the electrical energy storage cell barriersincluding layers of thermal insulating material and layers of elasticmaterial. In addition, electrical energy storage cell barriers have beenillustrated and described with reference to a combination of a layer ofelastic material and a layer of thermal insulating material, as well asa layer of thermal insulating material sandwiched between two layers ofelastic material. Again, these illustrations and descriptions are notintended to be exhaustive or to limit the embodiments to the preciseforms illustrated. For example, electrical energy storage cell barriersmay include more than the illustrated and specifically described numberof layers of thermal insulating material and layers of elastic material.

The above description of illustrated embodiments, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe embodiments to the precise forms disclosed. Although specificembodiments and examples are described herein for illustrative purposes,various equivalent modifications can be made without departing from thespirit and scope of the disclosure, as will be recognized by thoseskilled in the relevant art.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A method of manufacturing a portableelectrical energy storage device, the method comprising: providing,within a portable electrical energy storage device housing, a firstelectrical energy storage cell module including a plurality ofelectrical energy storage cells; providing within the portableelectrical energy storage device housing and adjacent the firstelectrical energy storage cell module, a second electrical energystorage cell module including a plurality of electrical energy storagecells; providing a thermal energy absorbing material in the housing; andproviding a sacrificial member within the housing and within the thermalenergy absorbing material, the sacrificial member formed of a materialthat does not thermally decompose when exposed to an environment below afirst temperature and thermally decomposes when exposed to anenvironment at a second temperature greater than the first temperature.2. The method of claim 1, further comprising locating the sacrificialmember between the first electrical energy storage cell module and thesecond electrical energy storage cell module.
 3. The method of claim 1,wherein the second temperature is greater than or equal to about 50° C.4. The method of claim 1, wherein the second temperature is greater thanor equal to about 60° C.
 5. The method of claim 1, wherein thedecomposed material has a volume that is at least 100% less than thevolume of the material before decomposition.
 6. The method of claim 1,wherein the thermal energy absorbing material is a phase changematerial.
 7. The method of claim 1, further comprising: providinganother sacrificial member formed of a material that does not thermallydecompose when exposed to an environment below a first temperature andthermally decomposes when exposed to an environment at a secondtemperature greater than the first temperature, the other sacrificialmember located between the portable electrical energy storage devicehousing and both the first electrical energy storage cell module and thesecond electrical energy storage cell module.
 8. A portable electricalenergy storage device, comprising: a first electrical energy storagecell module including a plurality of electrical energy storage cells; asecond electrical energy storage cell module including a plurality ofelectrical energy storage cells, the second electrical energy storagecell module positioned adjacent the first electrical energy storage cellmodule; a thermal energy absorbing material; and a sacrificial memberformed of a material that does not thermally decompose when exposed toan environment below a first temperature and thermally decomposes whenexposed to an environment at a second temperature greater than the firsttemperature, the sacrificial member located within the thermal energyabsorbing material.
 9. The portable electrical energy storage device ofclaim 8, wherein the sacrificial member is located between the firstelectrical energy storage cell module and the second electrical energystorage cell module.
 10. The portable electrical energy storage deviceof claim 8, wherein the second temperature is greater than or equal toabout 50° C.
 11. The portable electrical energy storage device of claim8, wherein the second temperature is greater than or equal to about 60°C.
 12. The portable electrical energy storage device of claim 8, whereinthe decomposed material has a volume that is at least 100% less than thevolume of the material before decomposition.
 13. The portable electricalenergy storage device of claim 8, wherein the thermal energy absorbingmaterial is a phase change material.
 14. The portable electrical energystorage device of claim 8, further comprising: a portable electricalenergy storage device housing, the first electrical energy storage cellmodule and the second electrical energy storage cell module locatedwithin the housing; and another sacrificial member formed of a materialthat does not thermally decompose when exposed to an environment below afirst temperature and thermally decomposes when exposed to anenvironment at a second temperature greater than the first temperature,the other sacrificial member located between the portable electricalenergy storage device housing and both the first electrical energystorage cell module and the second electrical energy storage cellmodule.
 15. A portable electrical energy storage device, comprising: aportable electrical energy storage device housing; a first electricalenergy storage cell module including a plurality of electrical energystorage cells and located within the portable electrical energy storagedevice housing; a second electrical energy storage cell module includinga plurality of electrical energy storage cells and located within theportable electrical energy storage device housing, the second electricalenergy storage cell module positioned adjacent the first electricalenergy storage cell module; a third electrical energy storage cellmodule including a plurality of electrical energy storage cells andlocated within the portable electrical energy storage device housing,the third electrical energy storage cell module positioned adjacent thesecond electrical energy storage cell module on a side of the secondelectrical energy storage cell module opposite from the first electricalenergy storage cell module; a thermal energy absorbing material; and asacrificial member within the thermal energy absorbing material, thesacrificial member formed of a material that does not thermallydecompose when exposed to an environment below a first temperature andthermally decomposes when exposed to an environment at a secondtemperature greater than the first temperature.
 16. The portableelectrical energy storage device of claim 15, wherein the sacrificialmember is located between the first electrical energy storage cellmodule and the second electrical energy storage cell module.
 17. Theportable electrical energy storage device of claim 15, wherein thesacrificial member is located between the second electrical energystorage cell module and the third electrical energy storage cell module.18. The portable electrical energy storage device of claim 15, whereinthe second temperature is greater than or equal to about 50° C.
 19. Theportable electrical energy storage device of claim 15, wherein thesecond temperature is greater than or equal to about 60° C.
 20. Theportable electrical energy storage device of claim 15, wherein thedecomposed material has a volume that is at least 100% less than thevolume of the material before decomposition.
 21. The portable electricalenergy storage device of claim 15, wherein the thermal energy absorbingmaterial is a phase change material.
 22. The portable electrical energystorage device of claim 15, further comprising: another sacrificialmember formed of a material formed that does not thermally decomposewhen exposed to an environment below a first temperature and thermallydecomposes when exposed to an environment at a second temperaturegreater than the first temperature, the other sacrificial member locatedbetween the portable electrical energy storage device housing and boththe first electrical energy storage cell module and the secondelectrical energy storage cell module.